Mixtures of borates containing active oxygen.



' rrio FRIEDRICH LUDW'IG SCHMIDT, 9F CI-IJXRLQTTENETEBG, GER-MANY,ASSIGNOR TO THE ROESSLER & HASSLACI-IER CHEMICAL COMPANY, A CORPORATIONOF NEW YORK.

MIXTURES OF BORATES CONTAINING ACTIVE OXYGEN.

No Drawing.

water at a temperature as low as 50 C.

This is a disadvantage in the application of sodium perborate as ableaching agent, inasmuch as the washing and bleaching process can onlyproperly begin at a higher temperature, so that a large proportion ofthe oxygen will be driven off and its effect lost before the eflicienttemperature is attained. In View of this fact, the discovery thatmagnesium perborate evolves its oxygen at a higher temperaturerepresented an advance. It is known that mixtures of sodium perborateand a magnesium salt in equivalent proportions can be employed forbleaching, instead of pure magnesium perborate. In this case themagnesium perborate is formed from the sodium perborate and themagnesium salt by double decomposition. The proportions which are usedin the latter process are such that the whole of the sodium perborate isdecomposed by the magnesium salt. To this extent the latter )rocess onlydiffers from that with magnesium perborate in the fact that themagnesium perborate is produced by the said double decomposition justbefore the bleaching occurs. While the employment of magnesium perboratefor bleaching purposes represents an advance as regards the bleachingeffect, owing to the greater stability of the magnesium perborate underboiling, yet on the other hand its high price militates against its Wideemployment.

We have found that it is possible to obtain the effect of greaterresistance to boiling with the cheap sodium perborate and with the otheralkali perborates containing active oxygen, by adding certain substancesto the same. To these substances belong also the salts of magnesium andtheir base magnesia itself.

The present invention, so far as it extends to the addition ofmagnesium, differs from the above mentioned process according to Whichsodium perborate is completely deapplication file-:1 January 25, 1910.

Serial No. 540.044.

composed by equivalent proportions of magnesium salt.

We have found that it is not necessary to add to the alkali perborate somuch magnesium compound that the whole bleaching process is carried outwith magnesium perborate, that is to say that all the sodium perborateis decomposed by. the magnesium salt. On the contrary, we have foundthat it is possible to attain the said efiect of greater resistance toboiling with only very small proportions of an addition of a mag nesiumcompound. For example, the addition of a fraction of a molecularproportion suffices to attain a very istinct effect, as will appear fromthe following :A one per cent. solution of sodium perborate boa;- ed to70-80 C. was found after a few minutes to have losthalf its activeoxygen and.

after twenty-five minutes only 10 per cent. of the oxygen remained. Whenl/Gth. of a molecular proportion of magnesium sulfate is added to onemolecular proportion of sodium perborate, dissolved to a one per cent.solution, about 98 per cent. of the. active oxygen remains aftertwenty-five minutes heating to 70-80 C. WVhen under the same conditionsl/lith. of a molecular proportion of magnesium sulfate is added, theeffect of this addition is that after twentyiive minutes heating to thesame temperature, about 95 per cent. of the oxygen remains. The additionof 1/60th. of a molecular proportion of magnesium sulfate under exactlythe same conditions has the effect that about T0 per cent. of the oxygenremains after the same period. It follows from these examples that inorder to attain a higher resistance to boiling it is not neces sary toconvert the alkali perborate com pletely into magnesium perborate, buton the contrary a very small molecular proportion of magnesium saltsuflices. This action of less than equivalent proportions of mag nesiumsalt was not to be foreseen, for in the new process the greater portionof the sodium perborate remains unaltered in solution, and the naturalassumption would therefore be that this unaltered sodium perborate wouldsplit off the oxygen just as readily as do ordinary solutions of sodiumperborate.

The new process utilizing only small quantities of magnesium saltpossesses another Patented Sept. 28, 1915.

important technical advantage over the known process using either readyprepared magnesium perborate or freshly formed magnesium perborate. Bothmagnesium perborate and. the magnesium borate into which the formerbecomes converted after the bleaching action are insoluble. There istherefore in the bleaching liquor a con-' siderable quantity of suchmagnesium prei? cipitate, which, owing to the large quantity present,has a detrimental effect and is difficult to remove from the bleachedgoods. By using smaller quantities of magnesium salt, far less of thistroublesome precipitate has to be dealt with, and the less the quantityof magnesium salt used the smaller is the quantity of the precipitate.

It has further been found that it is not only magnesium alone thatpossesses the described action, but that compounds of the alkaline earthmetals calcium, strontium,

barium. give the same action. This is illustrated by the followingexamples carried out under the same conditions as with the sodiumperborate, the heating being carried out at the same temperature of70-80 C. and the remaining oxygen being measured after twenty-fiveminutes. The addition of l/6th of a molecular proportion of chlorid ofcalcium is found to make the solution stable up to about 87 per cent,while l/50th of a molecular proportion of chlorid of calcium is found togive a stability of about 50 per cent. 1/l5th of a molecular proportionof strontium chlorid gives about 90 per cent. stability, 1/12th of amolecular proportion of barium chlorid about 80 per cent. stability. Thefixing efiect of the said sub stances applies not only to sodiumperborate, but also to the other borates containing It is not evennecessary that the salts or bases having an action in the describedsense shall be of the ordinary kind; for example the per-salts and'peroxids ofthe same will serve the purpose.

I wish to be understood that the term perborate is also to embrace otherborates containing active oxygen, as for instance perborax and suchborates, containlng active oxygen, as manufactured by the processcovered by U. S. Patent No. 1,006,? 98 issued to me.

What I claim is: 1. The-herein described new mixtures of boratescomprising a perborate and a soluble inorganic magnesium compound in aless than equivalent proportion, which give a superior. bleachingelfect.

2. The herein described new mixtures of borates, comprising a perborateand a soluble inorganic compound of an alkaline earth metal in a lessthan equivalent proportion which give a superior bleaching effect.

The said' fixing sub- 4' In witness whereof I have hereunto signed myname this sixth day of January, 1910,

in the presence of two subscribing Witnesses;

DR. FRIEDRICH LUDWIG SCHMIDT.

Witnesses WOLDEMAR HAUPT, HENRY HASPER.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Fatents, Washington, D. 0.

